Polychaetes (Bristle Worms)

Bristle worms are another group of the polychaetes. They are cylindrical, soft-bodied annelids with segmented bodies. They have bristles (setae) along both sides of their bodies along their entire lengthThey range in size from around 2.5 to 40 cm in length. Some burrow or build tubes, while others crawl or swim. Each species falls into one of two general categories:

• "Errant worms" that wander among the shoreline and shallows in search of food. Some may build tubes or burrows that they return to, while others move around freely.
• Sessile or sedentary worms that build permanent tube or burrow “homes” on shoreline flats. Since they wait for their prey to come to them, tube-building bristle worms have specialized appendages to help them gather food.

Bristle worm
Image © James van den Broek Flickr

Sedentary Bristle worms feed on plankton and other bits of organic matter, including algae or pieces of dead organisms. Others like fireworms, are carnivores feeding on colonial animals eg: sponges and ascidians.

Most bristle worms are either male or female. They reproduce by releasing sperm and eggs into the water. Larvae metamorphose from a free-swimming stage to a segmented stage before maturing. A few bristle worm species take care of their young.

In Fireworms, the bristles have become defensive organs. They are fragile, hollow tubes filled with poison. They are easily broken when the worm is touched and the pain they cause when they pierce the skin makes their common name very appropriate.

Fire worm
Image © Ken Traub Flickr

References

www.reefcorner.com/SpecimenSheets/bristleworm.htm
http://en.wikipedia.org/wiki/Polychaete
www.seaslugforum.net/find/polychaete
www.allaboutworms.com/bristle-worm
www.chesapeakebay.net/bfg_bristle_worms.aspx
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